Devices for opening and supporting a headway in a closed excavation are known which comprise a blade envelope consisting of blade heads and blade tails adjoining the latter. The entire blade envelope is held upon the advance by support frames. The individual support frames in the event of an open development of the blade envelope, for instance of horseshoe-shaped cross section, conduct their forces into the floor while they support the individual blade heads or blade tails. When the blade envelope is of closed cross section, the support forces counteract each other in the frames. Upon the opening, the blades are driven forward individually or in groups and the support frames are correspondingly lowered in order to follow the blade envelope in the opening direction. For the final supporting or support of the headway, a formwork device, which is also frame-shaped and has formwork elements in the end region of the blade tails, is provided. The second device serves here as inner formwork and is arranged with its outside at a distance from the rock or ground which corresponds to the inside diameter of the tunnel shell. The blade tails in this connection form the outer formwork. The supporting is effected in the manner, for instance, that concrete is introduced into the space between the bottom of the blade tails and the top of the formwork device. Upon the advance of the blade envelope, a space of a height corresponding to the thickness of the blade tails is produced between the layer of concrete and the rock or bottom. Since the blade tails serve in the region of the final supporting on the one hand as outer formwork and on the other hand support the opened tunnel cross section, said space must be filled for instance with concrete or granulate and compacted upon the advancing of the blades in order that the soil cannot cave into the space. The concrete which is to be introduced into the space is fed via conduits, each of which discharges into an outlet opening in the region of the end of the blade-tail on the rear closure edge thereof. Such a known device is used for loose soils.
In the case of firm soils, such as stone or massive rock, the tunnel opening is first predrilled and then lined with concrete by means of a sliding formwork. Such a sliding formwork can comprise supporting frames on which individual formwork sections rest, the outer guide of the entire formwork device being tapered slightly conically from front to rear as seen in the direction of advance in order to avoid constraints in the freshly concreted region along the individual formwork sections upon the advance thereof. If, namely, irregularities have been produced in the concrete, for instance by thickness tolerances and/or saggings of the sections under load in their longitudinal direction and thus constraints are exerted on the fresh concrete, such constraints would lead to considerable damage without the conical tapering. In the case of such a sliding formwork, the formwork sections serve as internal formwork elements or internal formwork sections while the firm soil serves as outer formwork. The concrete is forced, seen in the direction of advance, on the frontmost end of the slide formwork into the correspondingly sealed intermediate space, the tunnel shell which has already been lined with concrete serving as abutment.
The object of the present invention is to propose a device for the opening and supporting of a headway in closed or open excavations in soils which are not suitable for a predrilling of the tunnel opening, in which the final supporting can take place directly in the region of the blade envelope without a further formwork device having to be provided.